New Trier High School Stomach Flu Outbreak Presumed to Be Norovirus

WINNETKA, Ill. (WBBM)  — About 120 students and staff got sick at New Trier Township High School in Winnetka [MAP/SAT] last week.
The high school was thoroughly cleaned last weekend. Door knobs, stairwell railings and other surfaces that are frequently touched were treated with a cleaning agent specifically designated to kill the norovirus.

The common ailment names associated with norovirus are winter vomiting disease, viral gastroenteritis, acute nonbacterial gastroenteritis, food poisoning (incorrectly), and stomach flu.

The disease is usually self-limiting, and characterized by nausea, vomiting, diarrhea, and abdominal pain. General lethargy, weakness, muscle aches, headache, and low-grade fever may occur. Symptoms may persist for several days and may become life-threatening in the young, the elderly, and the immune-compromised if dehydration is ignored or not treated.

Specific diagnosis of Norovirus is routinely made by broadly reactive conventional polymerase chain reaction (PCR) assays from stool samples which more recently were replaced by real-time PCR assays, which give results within a few hours. Furthermore, these assays are very sensitive and can detect concentrations as low as 10 virus particles per assay. Apparently no students or staff submitted samples for the lab to test.

Less technically demanding assays such as ELISA assays based on antibodies against a cocktail of different virus-like particles are commercially available but have been reported to lack both specificity and sensitivity.

Hand washing remains an effective method to reduce the spread of Norovirus pathogens.  Surface sanitizing is recommended in areas where the Norovirus may be present on surfaces. Though isopropyl alcohol has been proven to be an effective sanitizer against other viruses, the CDC recommends using alcohol-based sanitizers in conjunction with hand washing to reduce the spread of Norovirus.

Norovirus can be aerosolized when those stricken with the illness vomit. Norwalk gastroenteritis is also transmitted by the fecal-oral route from contaminated water and foods. A CDC study of eleven outbreaks in New York State lists the suspected mode of transmission as person-to-person in seven outbreaks, foodborne in two, waterborne in one, and one unknown. The source of waterborne outbreaks may include water from municipal supplies, wells, recreational lakes, swimming pools, and the often overlooked culprit, ice machines.

Shellfish and salad ingredients are the foods most often implicated in Norwalk outbreaks. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with the Norwalk virus. Foods other than shellfish are contaminated by ill food handlers.

Norovirus is often a problem on cruise ships. In 2002, there were 25 reported outbreaks, with 2,648 passengers becoming ill from the virus. Outbreak investigations by the U.S. Centers for Disease Control and Prevention have shown that transmission among cruise ship passengers is almost wholly person-to-person. Cruise ship water supplies have never been implicated.